1. Field of Invention
The present invention relates to fluid dynamic bearing motors and, more specifically, to a multi-journal fluid dynamic bearing motor assembly.
2. Description of Related Art
FIG. 1 provides a perspective view of a disc drive assembly 150. In this arrangement, a plurality of discs 110′ are stacked vertically within the assembly 150, permitting additional data to be stored, read and written. The drive spindle 151 receives the central openings 105 of the respective discs 110. Separate suspension arms 156 and corresponding magnetic head assemblies 158 reside above each of the discs 110. The assembly 150 includes a cover 130 and an intermediate seal 132 for providing an air-tight system. The seal 132 and cover 130 are shown exploded away from the disc stack 110′ for clarity.
In operation, the discs 110 are rotated at high speeds about the spindle 151. As the discs 110 rotate, an air bearing slider on the head 158 causes each magnetic head 158 to be suspended relative to the rotating disc 110. The flying height of the magnetic head assembly 158 above the disc 110 is a function of the speed of rotation of the disc 110, the aerodynamic lift properties of the slider along the magnetic head assembly 158 and, in some arrangements, a biasing spring tension in the suspension arm 156.
A servo spindle 152 pivots about pivot axis 140. As the servo spindle 152 pivots, the magnetic head assembly 158 mounted at the tip of its suspension arm 156 swings through arc 142. This pivoting motion allows the magnetic head 158 to change track positions on the disc 110. The ability of the magnetic head 158 to move along the surface of the disc 110 allows it to read data residing in tracks along the magnetic layer of the disc. Each read/write head 158 generates or senses electromagnetic fields or magnetic encodings in the tracks of the magnetic disc as areas of magnetic flux. The presence or absence of flux reversals in the electromagnetic fields represents the data stored on the disc.
Fluid dynamic bearings tend to generate less vibration and non-repetitive run-out in the rotating parts of motors than ball bearings and other types of bearings. For this reason, fluid dynamic bearing motors are oftentimes used in precision-oriented electronic devices to achieve better performance. For example, using a fluid dynamic bearing motor in a magnetic disc drive, such as magnetic disc drive 150 described above in conjunction with FIG. 1, results in more precise alignment between the tracks of the discs and the read/write heads. More precise alignment, in turn, allows discs to be designed with greater track densities, thereby allowing smaller discs and/or increasing the storage capacity of the discs.
As persons skilled in the art are aware, an ongoing challenge in fluid dynamic journal bearings is balancing the tradeoff between motor performance and power consumption. For example, increasing the stiffness of the fluid dynamic journal bearings results in less vibration in a motor's rotating parts and, therefore, increased motor precision and performance. However, an increase in the stiffness of the bearings is usually accompanied by an increase in the power consumption of the motor. Therefore, there exists a need for a technique to increase the stability of a fluid dynamic bearing without increasing the amount of power consumed by the fluid dynamic bearing.